Atmospheric Oxidation Mechanism of Methyl Acetate

Smog chamber/FTIR techniques were used to study the Cl atom initiated oxidation of CH 3 C(O)OCH 3 in 700 Torr of N 2 /O 2 at 296 K. Relative rate techniques were used to measure k (Cl+CH 3 C(O)OCH 3 ) = (2.2 ± 0.3) × 10 -12, k (Cl+CH 3 C(O)CH 3 ) = (2.2 ± 0.4) × 10 -12, k (Cl+CH 3 C(O)OC(O)H) = (1.0 ± 0.1) × 10 -13, and k (Cl+ ClCH 2 C(O)OCH 3 ) = (8.5 ± 1.9) × 10 -13 cm 3 molecule -1 s -1 . The reaction of Cl+CH 3 C(O)OCH 3 was found to proceed more than 95% via H-abstraction at the −OCH 3 site. The fate of the CH 3 C(O)OCH 2 O· radical was studied in 700 Torr of N 2 /O 2 diluent at 296 K in the absence and presence of NO. Two loss mechanisms were identified: reaction with O 2 to give CH 3 C(O)OC(O)H and α-ester rearrangement to give CH 3 C(O)OH and HCO· radicals. It was found that α-ester rearrangement is more likely when CH 3 C(O)OCH 2 O· radicals were produced via the CH 3 C(O)OCH 2 O 2 · + NO reaction than when they were produced via the self-reaction of peroxy radicals. In one atmosphere of air ([O 2 ] = 160 Torr) containing NO at 296 K it can be calculated that 65 ± 14% of the CH 3 C(O)OCH 2 O· radicals undergo α-ester rearrangement while 35 ± 5% react with O 2 .